This invention relates to the polymerization of alpha-olefins and more particularly to an improved catalyst for the polymerization of alpha-olefins and methods for the preparation and use thereof.
In the polymerization of alpha-olefins, it is desirable to employ catalysts having sufficiently high activities that useful products can be obtained without the need for separation of catalyst residues from the polymeric product. A number of catalysts generally comprising a promoter and a supported, transition metal-containing component have been proposed for this purpose. One such catalyst, disclosed in U.S. Pat. No. 3,875,075 (Boone et al.), comprises (A) an organoaluminum promoter and (B) a supported component prepared by reaction of (1a) a magnesium salt of a chlorine-substituted C.sub.2-7 carboxylic acid such as magnesium trichloroacetate, or (1b) the reaction product of (1a) with an aluminum halide, with (2) a Group IVB or VB halide or haloester, preferably titanium tetrachloride, at about 25.degree. to 200.degree. C., preferably in an inert diluent. While such catalysts exhibit desirable activities and sufficiently high sensitivity to molecular weight control agents such as hydrogen to allow for preparation of a wide range of product grades, preparation of the (B) component is disadvantageous because a substantial excess of the Group IVB or VB component typically is required to attain catalyst components having suitable activities. See Boone et al. of Column 3 lines 29-39. Further, the reaction product of the chlorocarboxylate salt or chlorocarboxylate salt-aluminum halide reaction product with the halogenated Group IVB or VB compound contains not only Group IVB or VB compounds affixed to a magnesium-containing support, but also, loosely adhering Group IVB or VB compounds. The latter, if retained in the product during use in the polymerization of alpha-olefins, can have undesirable effects on polymer particle size and morphology. Accordingly, it is desirable to wash the reaction product with an appropriate solvent to remove loosely adhering Group IVB or VB compounds prior to polymerization use and the patentee so indicates at Column 3 lines 40-46. As can be appreciated washing of the reaction product is disadvantageous because it adds expense to the preparation.
It is an object of the present invention to provide a supported catalyst component and catalyst based thereon which avoid the aforesaid difficulties. A further object of the invention is to provide an improved alpha-olefin polymerization catalyst and methods for the preparation and use thereof. Other objects of the invention will be apparent to persons of skill in the art from the following description.
It has now been found that the foregoing objects can be attained according to the present invention wherein there is provided an improved, supported catalyst component comprising the reaction product of components comprising (1) at least one divalent metal halocarboxylate salt, (2) at least one oxygenated organic compound of a Group IVB or VB metal, (3) at least one organoaluminum component, and, when (3) contains less than an effective amount of halogen, (4) at least one halogenating agent other than a halogen-containing compound of a Group IVB--VIB metal. In addition, there is provided an improved catalyst comprising (A) a promoter and (B) the aforesaid supported component. In the polymerization of alpha-olefins, such catalysts exhibit sufficiently high activities as to eliminate the need for separation of catalyst residues from polyalpha-olefins produced in the presence thereof. Further, such polyalpha-olefins exhibit a useful range of molecular weights and the catalysts exhibit sufficient sensitivity to molecular weight control agents commonly used during polymerization to allow for tailoring of product molecular weights to various end uses. Advantageously, preparation of the invented components does not require the use of large excesses of Group IVB or VB component and there is no need to remove unreacted Group IVB or VB compounds from the reaction product as required by Boone et al. The invented catalysts are advantageous for the additional reason that a mixture of divalent metal halocarboxylate salt with oxygenated organic Group IVB or VB component can be dissolved in an inert liquid preparative medium to form a one-phase system and thereby facilitate subsequent preparative manipulations.
Other patents which disclose supported catalyst components which may be of interest with respect to the present invention are discussed hereinbelow.
U.S. Pat. No. 3,658,722 (Delbouille et al.) discloses supported catalyst components prepared from (1) a nonmetallic halogenating agent, (2) an oxygenated compound of a divalent metal, including "salts derived from monoor polycarboxylic acids" (Column 2 lines 60-65), and (3) a Group IVB--VIB halide, alkoxide, or alkoxyhalide. Such components can be reacted simultaneously or the halogenating agent and the oxygenated divalent metal compound can be reacted in a first step followed by reaction of the result with the Group IVB--VIB component. To like effect is British Pat. No. 1,321,766 (Solvay) although a broader range of halogenating agents is disclosed. The invented catalysts are disguishable from those of Delbouille and Solvay because neither patent discloses the use of halocarboxylate salts of divalent metals in preparation of supported catalyst components. Further, neither patent discloses the use of organoaluminum components during the preparation. Additionally, like the aforesaid Boone et al. patent, Delbouille and Solvay require treatment of the disclosed reaction products "to eliminate the transition metal compounds which have not been chemically bonded to the support . . . preferably . . . by washing with hexane or with any other volatile inert solvent." (Debouille et al. at Column 4 lines 24-28; also see Solvay at page 3 lines 87-97.)
U.S. Pat. No. 3,901,863 (Berger et al.) discloses supported catalyst components prepared from (1) oxygenated organic transition metal compounds including titanium alkoxides, phenates, and enolates, (2) oxygenated organic compounds of divalent metals, including salts of carboxylic acids, and (3) organoaluminum halides of the formula A1R.sub.n R'.sub.3-n wherein R is a hydrocarbyl radical of 1 to 20 carbon atoms, R' is halogen, and 0.ltoreq.n.ltoreq.3. The disclosed catalyst components preferably are prepared by simultaneous reaction of the components or by reaction of the organoaluminun halide component with a mixture of the oxygenated organic components or by reaction of the oxygenated organic divalent metal compound with a mixture of the transition metal compound and the organoaluminum halide. Column 5 lines 1-19. Although Berger et al.'s oxygenated organic divalent metal compounds include carboxylate salts, halocarboxylate salts are not disclosed.
U.S. Pat. No. 3,984,389 (Delbouille et al.) discloses supported catalyst components prepared by reaction of divalent metal salts of hydrated, hydrous, or water-containing carboxylic acids and halogen-containing compounds of the Group IVB--VIB metals followed by washing of the result. The use of halocarboxylate salts of divalent metals, oxygenated organic compounds of the Group IVB and VB metals, organoaluminum components and halogenating agents according to the present invention is not disclosed.
British Pat. No. 1,258,984 (Hoechst) discloses supported catalyst components prepared from magnesium carboxylates and halogen-containing titanium compounds. However, halocarboxylate salts are expressly excluded at page 3, line 121 and the patentee fails to disclose the use of the Group IVB and VB and organoaluminum components employed in preparation of the invented catalyst components.